Engine compression release method and apparatus

Abstract

The present invention comprises apparatus and methods for releasing internal combustion engine compression during cranking to reduce cranking effort and the size and weight of the starter motor and battery. It is particularly suitable for fuel conservation systems that stop the engine when the vehicle is stopped in traffic, and restart the engine when the driver steps on the accelerator petal, since such systems place heavy demands on the starter motor and battery. The apparatus provides a means for automatically shifting the valve gear such that exhaust and / or inlet valves are held slightly open during the intake compression strokes to reduce compression torque during initial cranking, and restoring the valves to normal operation before the first firing event. The method provides a sequence of steps executed by the engine electronic control module to control the compression release apparatus to carry out the engine starting process safely and reliably.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. provisional application Ser. No. 61 / 687,835 filed May 2, 2012.FIELD OF THE INVENTION[0002]The present invention is related to methods and apparatus for temporarily reducing the compression pressure in reciprocating internal combustion engines during startup cranking, thereby reducing the cranking torque and energy required from the engine starting system. In particular, it is related to such methods and apparatus applicable to multi-cylinder vehicle engines that may be stopped and started frequently to reduce the fuel consumed while the vehicle is not moving.BACKGROUND OF THE INVENTION[0003]Significant fuel consumption savings may be gained in city driving by stopping the engine while the vehicle is stopped, and cranking and re-starting the engine automatically when the driver steps on the accelerator pedal. This repetitive cranking, however, places high torque and energy demands on the starting...

AI Technical Summary

Benefits of technology

The present invention is about a method for starting an engine using a process called compression release. This method involves controlling the movement of the valves in the engine to allow them to open slightly during the compression and expansion strokes, and then close completely at the start of the engine's piston movement. This allows for easier starting of the engine, while also improving fuel efficiency. The invention also includes systems and apparatus for carrying out this method.

Problems solved by technology

This repetitive cranking, however, places high torque and energy demands on the starting system, typically a battery powered electric motor, leading to larger and more costly batteries and motors than are required for less frequent use.

The exhaust valves reclose before ignition, since combustion pressure force on partially open exhaust valves would place unacceptably high stresses on the valve gear rather than carrying the force safely on the seat of the closed valve.

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